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Help. Engine popped when turning over by hand

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Today we put the heads on the engine. Then I proceeded to put the lifters in, and started setting the rockers up. I went to turn the engine over to TDC on #1, and it really didn’t want to move... so much it started to rotate the engine on the stand. I put the pin into the engine stand to prevent rotation, and tried again. It finally came free, but with a sickening SNAP.  No idea really what it was. I did see what looked like a puff of smoke (it wasnt) come out the distributor hole. Almost as if something stuck had been knocked free. I can’t imagine what it is.  Also, when I would turn the engine, I got this odd noise heard here:

It kinda sounds like a spring being wound tight.  anybody have any thoughts?

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Get the sump off - only way you will see what’s come adrift.  Something has gone wrong down in there and it will cost a lot more if you proceed to start up..

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Survey says... misaligned timing gears. I pulled the pan (for the 3rd time) and could see the timing chain pop back into place with the noise, plus the crank sprocket is clearly not back all the way. 

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Some stuff in the pic I posted that might be useful as a double check ?  Fuel pump eccentric, cam dowel, large washer keeping cam & dowel in place, keyway positions, crank sleeve, chain tension and the missing oil slinger.  Brian

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On 6/1/2019 at 5:38 AM, Brian Conway said:

Could you rotate the engine before you installed the heads ?  Just trying to narrow down the possibilities.  Brian

 I'm curious to this question. Or did you even spin the crank only when installed and torqued down, and when the pistons were installed the crank had to be rotated. Any noise then?

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On 6/2/2019 at 1:27 PM, RPM said:

 I'm curious to this question. Or did you even spin the crank only when installed and torqued down, and when the pistons were installed the crank had to be rotated. Any noise then?

I spun the crank without the pistons. Spun nice. I remember because I showed my son. 

I didn’t turn the engine over after I installed the timing set until I went to do rockers.  By that time it was all buttoned up.

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Question on the slinger.  I had to replace the cam in the engine but rebuilt it with the same timing gears and chain.  Was working fine.  Now starting the engine I get a metallic rub in one spot as the engine rotates.  I can hear it rotating by hand.   Does it with the engine running also (ran for only a few seconds).

Same crank, gears and cover.  Not sure what the rub sound is?  Slinger maybe?

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Did you check the alternator arm relative to the crank pulley?  I did that.  Have an aftermarket chrome set of brackets.  Just the clearance in the hole allowed the bracket to rub on the crank pulley but only in one spot.  Not sure how far along you are on the build.

I have a the slinger on a double row set of timing gears with no issue.  

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